1. Field of the Invention
The present invention relates to a linear motion guiding apparatus in which a passage forming member formed of resin is built into a body of movable member.
2. Description of the Related Art
The applicant has already proposed a technical idea that, in a movable block of a linear motion guiding apparatus, a pair of ball passage forming portions extending along the opposite longitudinal sides of a loaded-ball running groove, a ball returning passage forming portion and a pair of direction changing passage-inner guide forming portions were integrally formed of resin with a body of the movable block (refer to Japanese Patent Provisional Publication No. H7-317,762).
More specifically, when a resin forming is carried out, the body of the movable block is inserted in a die, and the ball passage forming portions, the direction changing passage-inner guide forming portions or the ball returning passage forming portion is integrally formed with the block body.
In the conventional movable block obtained by the integral forming, the block body is inserted in the die, as mentioned above. When the block body has a large size, a large-scaled die is required to be used. It is not easy to prepare such a large-scaled die, and there is actual restriction in size. The ball passage forming portions located at the opposite longitudinal sides of the ball running groove extending along the longitudinal direction of the block body are thin and long, with the result that molten resin may not reach every part of the space for forming the ball passage forming portions during the resin forming treatment.
Increase in number of gates formed on the die may solve the above-mentioned problem of misrun of the molten resin. However, when the block body is inserted in the die, the block body may deteriorate the run of the molten resin.
When the movable block has a pair of wing portions, which face right and left-hand side portions of the guide rail so that the guide rail is held between the wing portions, and there are four trains of balls between the right and left-hand side portions of the guide rail and the right and left-hand wing portions of the moving block, and more specifically, the upper and lower trains of balls are arranged at each of a gap between the right-hand side portion of the guide rail and the corresponding right-hand wing portion of the moving block and another gap between the left-hand side portion of the guide rail and the corresponding left-hand wing portion of the moving block, the block body inserted in the die may deteriorate the run of the molten resin in the width direction of the moving block.